The present invention, in some embodiments thereof, relates to a multimeric peptide and, more particularly, but not exclusively, to a dimer comprising a Placental Immunoregulatory Ferritin (PLIF) amino acid sequence which is useful for the treatment of cancer.
Placenta Immunomodulatory Factor (PLIF) is a protein composed of 165 amino acids. Of these, 117 match the ferritin heavy chain sequence, whereas the C-terminal 48 amino acids (C48) has a sequence which is not related to ferritin. It has been shown that the subcloned recombinant C48 peptide exhibits the bioactivity and therapeutic properties of PLIF [Moroz et al, J. Biol. Chem. 2002, 277, 12901-12905].
PLIF is expressed in the feto-maternal interface in both decidual mononuclear cells and syncytiotrophoblast cells. C48/PLIF binds to macrophages and activated T cells, inducing high levels of IL-10, and acts as a regulatory cytokine. It governs the balance between Th1/Th2 cytokines, which is essential for induction of tolerance during pregnancy. A significantly high correlation was observed between low levels of serum PLIF and the different pathological pregnancy conditions: early pregnancy failures; pregnancies complicated with abortion; intrauterine growth restriction (IUGR); and women at risk for developing pre-eclampsia.
Vaccination of mice with C48 (the bioactive domain of PLIF) prior to mating prevented pregnancy development (immune contraceptive), providing further evidence for the major role of PLIF in in vivo immune regulation. Further, in pregnant mice, neutralization of PLIF in vivo by passive transfer of anti-C48 antibodies (daily injections), starting at 3.5 days post-coitum, resulted in high embryo resorption rate, placental and embryonic growth restriction without affecting embryo organogenesis. This was accompanied by a significantly increased secretion of INF-γ and IL-12 (Th1) cytokines known to interfere with pregnancy outcome.
Thus, PLIF may be viewed as a major regulatory cytokine governing the Th1/Th2 cytokine balance and suppressor Tr cells, essential for induction of tolerance during pregnancy.
Further experimental studies on the immune regulatory function of PLIF/C48 in human bone marrow cells revealed that C48/PLIF exhibited growth of bone marrow myeloid progenitor cells concomitantly with T cell suppression. This was due to its dual regulatory effect on the cytokine chemokine network. Thus, C48/PLIF has proven to be a novel bifunctional therapeutic modality which enabled successful allogeneic bone marrow transplantation with long lasting tolerance.
It was reasoned that tumor cells may activate and use the above immunosuppressive mechanism, resembling those in the placenta, which prevent rejection of the embryo, and thereby enable tumor growth. Indeed, it has been shown that PLIF is upregulated and expressed in malignant cells such as Hodgkin's and non-Hodgkin's lymphoma, acute lymphatic leukemia (ALL), human breast cancer tissues, and breast cancer cell lines (T47D and MCF-7), but not in benign breast disease. Similar to the embryo, PLIF manipulates the cytokine network and immune response, enabling immune escape.
Experiments have been performed to restore T cell immunity and induce rejection of breast cancer by neutralizing C48/PLIF. Rabbit anti-C48 polyclonal antibodies injected intraperitoneally (i.p.) into immune compromised Nude mice engrafted with MCF-7 human breast cancer cells resulted in growth arrest associated with human cell apoptosis and massive intra-tumor lymphocytic infiltration. This was accompanied by activation of INF-γ, thus affecting the cytokine network and leading to breakdown of tolerance.
Additional background art includes U.S. Pat. No. 4,882,270 which discloses a method for detecting breast cancer, by using antibodies against isoferritin placental protein.
U.S. Pat. No. 7,217,686 discloses the amino acid sequence of the 48 amino acid peptide of PLIF.